Elsie is a shinigami who was assigned to capture evil spirits that have escaped from hell and is the Deuteragonist of the story. She is shown to have a very sweet, pure and innocent personality and often tries to please Keima's expectations as a "little sister" though often fails due to the cultural differences between them and how her endeavors usually leave Keima in a bad situation. She is fairly popular among young males, apparently more people (primarily boys) began coming when she began working in the family's cafe, such that Keima's mother once had her dress as a maid to attract more customers on the ground that no-one could resist her when she's wearing it (from the reactions around her while she's wearing it and after she takes it off it can be inferred to be true). Her feather cloth (the floating scarf she is always seen with) can change the appearance of an object, create disguises to aid the mission or it can hide people in plain sight. She is left-handed and is rarely seen without her broom, which she had for 298 years, as it was from her original role as a cleaner for hell. She reveals that she has an older sister that was very famous and was known as the "Demon of Demons". Ironically, despite being a demon, she is shown to have an incredible fear of ghosts and the dark.

To stay close to Keima, she tells Mari, Keima's mother, that she is an illegitimate child of Keima's father (nearly getting his parents divorced), and ends up living in the Katsuragi household as well as attending the same class in school.